When Sonnet say their 550W enclosure is not suitable for Vega64...

When Sonnet (and Apple) say that the Sonnet Breakaway Box 550W enclosure is not suitable for the Radeon Vega64... is that because it would have to cope with the scenario where the GPU is cranking flat out AND a laptop is expecting to charge itself simultaneously by pulling 87W out of the TB3 port?

If, rather than a laptop, it's a Mac Mini being used (which has its own AC power at all times), then it seems to me that the 550W version should cope with a Vega64 just fine.

Do you agree?

As I understand it, computer industry rules are that a graphics card with dual-8-pin power cables is allowed to draw 75W from the PCIe slot plus 300W from the cables... plus maybe a touch extra by being cheeky and relying on tolerances. So let's say actual power consumption would be 400W max for the Vega64, in addition to whatever the Thunderbolt chipset itself consumes?

(The reason I ask is because the Sonnet 550W version is significantly less expensive than the 650W where I am).